I seem to have found a fix, mentioned by Neil Smith at https://github.com/apache/netbeans/issues/5110
Some options need to be added to run.args.extra. So my project.properties file now contains:
run.args.extra=-J--add-opens=java.base/java.net=ALL-UNNAMED -J--add-exports=java.desktop/sun.a
I continue to get execeptions on a NB platform app startup despite including --add-opens as I have seen posted in several places.
I have struggled with this for longer than I would like to admit, I hope someone can please help me resolve.
I am running NB19-rc5 (same was happening on NB16) and
